Satish Kumar, a post-graduate student of Himachal Pradesh University, fainted during the strike and was taken to the varsity's health centre, prompting SFI activists to block a road in the campus.
He was then referred to Indira Gandhi Medical College and was in a bad condition, an SFI release claimed.
The activists have been sitting on a relay hunger strike for the past 30 days pressing for reversal of the rustication of seven students by the varsity and a roll-back of fee hike, among other demands.
He cautioned that no administrative officer of the University would be allowed to enter the campus in case "anything wrong happens" to the sick student.